This invention relates to fluid-film bearings for rotating machinery and more particularly to adjustable clearance journal bearings for efficient support of high speed rotors, which include resilient bearing-inserts as well as a method for fabricating the resilient inserts.
Rigid and rigidly-mounted fluid-film bearings are limited in regard to rotor speed and mass and are prone to cause the motion of the rotor to become unstable due to self-excited whirl. The instability and associated growth of rotor excursions results in vibrations which frequently lead to damage and destruction of these bearings and of the machinery associated therewith. Furthermore, such bearings are not tolerant of misalignment, thermal distortion or foreign particles. These shortcomings are particularly pronounced in gas-lubricated bearings, which also lack the greater damping and boundary lubrication provided by the more viscous liquid lubricants.
Methods of increasing the stable operating range of rigid gas bearings have been the subject of numerous investigations and publications in the literature. Partial flexibility, and with it improved stability and self-aligning characteristics, can be provided by pivoted-shoe bearings, but these are generally complex, expensive and tend to introduce other problems, such as pivot fretting and wear, shoe flutter and other dynamic problems. Furthermore they are difficult to install and generally require the spring loading of a shoe, if stability is to be insured.
Considerable progress in overcoming the above shortcomings has been achieved through the introduction of flexible-element bearings, known as "foil bearings". Journal bearings of this type are shown in various U.S. Patents. Trumpler No. 1,595,744; Marley No. 3,382,014; Barnett No. 3,677,612 and Licht No. 3,795,427, for example, show bearings which utilize overlapping, flexible foils or reeds disposed about the journal. Falk et al No. 2,703,735; Marley No. 3,434,761; Licht No. 3,520,578 and British Pat. No. 296,132 to Gray illustrate journal bearings which utilize one or more tensioned bands or foils disposed about the journal.
Cherubim U.S. Pat. No. 3,809,443 shows two foil elements welded together, one as a backing with circular arches convex toward the journal and the other as a plain foil element supported on the crests of the arches. The flexibility of such arches is limited and the inherent damping is frequently insufficient to suppress instability, since lateral motion (rubbing) between foil members is constrained. The method of joining poses additional problems.
Licht U.S. Pat. No. 4,133,585, incorporated herein by reference, describes a single foil element in which a polygonally bent backing with radiused vertices forms a resilient support and is integral with the plain section of the foil. The backing and the plain section are coiled and retained in a simple manner in the bearing shell.
Although prior art foil bearings have proven useful, the need for further improvements has remained. There is an unquestioned need for improved resilient, gas or liquid lubricated journal bearings for high-speed rotors in numerous applications, such as turbocompressors, turbochargers, turbogenerators, turbine gas generators, aircraft cabin air-conditioning units, cryotenic expanders and gas liquefaction machines, rotating-mirror scanners, blowers, pumps, centrifuges, yarn processors and spinners and the like.